Cold-walled vessel process for compounding, homogenizing and consolidating semiconductor compounds

ABSTRACT

A method is provided for compounding, homogenizing and consolidating compounds. In one embodiment, the charge components are mixed in a controlled addition process, then the newly-formed compound is heated to become totally molten, followed by a rapid quench at room temperature. In an alternate embodiment, the components are supplied with an excess of one component acting as a solvent, heated to dissolve additional components, and then the solvent is separated from the compound to produce homogeneous consolidated compounds. The methods herein are advantageously applied to provide an economical and fast process for producing CdTe, CdZnTe and ZnTe compounds.

TECHNICAL FIELD

The present invention relates generally to a method and apparatus forforming a compound semiconductor crystal and, more particularly, to amethod and apparatus for compounding, homogenizing and consolidatingsemiconductor compounds, especially Cadmium Zinc Telluride (“CdZnTe” or“CZT”) or Cadmium Telluride (“CdTe”) in accordance with using acold-walled vessel.

BACKGROUND OF THE INVENTION

There is a wide range of ternary and quaternary II-VI and III-Vsemiconductor compounds, which are difficult to grow into high qualitysingle crystals from the melt. Principally, there are these fourreasons: very high melting points, non-congruent melting, decompositionor evaporation on melting or having a melting point above the desirablecrystallographic phase.

For example, totally molten CZT requires a temperature in excess of1100° C. (above its liquidus temperature). A hot-walled or a vesselunder high inert gas pressure is thus required to prevent the molten CZTfrom decomposing/subliming to the cooler locations. Such pressures mayexceed 100 atmospheres, requiring expensive reactors.

Several growth methods have been used for the growth of bulk CZT. Theseinclude Horizontal Bridgman (HB) and Vertical Bridgman (VB) or VerticalGradient Freeze (VGF) in sealed systems; High Pressure Vertical Bridgman(HPVB) in unsealed ampoules; the Traveling Solvent Method (TSM) and theTraveling Heater Method (THM).

Limitations of Current Art

There are many limitations and problems with Bridgman-type melt growthmethods. Varying gradients and uncontrolled temperature fluctuations atthe crystal growth interface serve to induce crystal defects andinhomogeneities. Processes requiring fused sealed ampoules or “closedtubes” incur the additional cost burden of single-use ampoules.Specifically for CZT, the Bridgman VGF method produces large axialvariations in Zn concentration, because of the non-congruent meltingproperty. Additionally, the relatively long temperature ramps and slowgrowth rate again increase the cost of forming CZT by this method.

The reaction to compound CZT from elemental Cd, Zn and Te is highlyexothermic and unstable. It can occur unpredictably with explosiveforce. The consequence of such explosions may include damage to theapparatus, loss of expensive reagents, distribution of toxic materialsinto the environment and risks to those personnel in the vicinity. Tomitigate against these effects expensive explosion-proof apparatus andfacilities are necessary.

The three constituents, Cd, Zn and Te, each have different meltingpoints below the melting point of CZT. As the temperature reaches therange ˜600-900 C unreacted liquid Te, liquid Cd and liquid Zn attempt tocoexist with solid CZT already formed through the reaction of thecomponents. As the temperature rises various reactions continue to occurbetween liquids and solids and between liquids and liquids to form otherliquid or solid intermediaries or the desired CZT end product. Themixture is highly heterogeneous in terms of the solid, liquid and vapourphases and in terms of the temperature distribution in the reactionvessel. The rate of reaction is influenced both by the chance contact ofreagents and intermediate compounds and by the extent of the heatgenerated—raising the local, and therefore the average, temperature andfurther accelerating the reaction. Very high Cd vapour pressures canoccur, for example, if unreacted elemental Cd is suddenly heated to ahigh temperature.

The high temperatures for long periods typical in melt growth processescan cause oxides to build up on the boule surface, resulting in theboule adhering to the walls of the containment vessel, such as a quartzampoule. This may cause difficulty in releasing the boule from thevessel. Additionally. due to the high temperatures of ˜1100° C. at peakand for an extended duration in conventional CZT compounding processescontaminants can leach from the quartz ampoule.

Typically, sealed ampoules used in VGF compounding processes require aportion of the sealed ampoule to be cut off to extract the boule,causing waste and possibly precluding reuse of the ampoule. The VGFampoules must be evacuated to high vacuum and use a quartz/quartz fusedseal. If a slow leak occurs during the subsequent heating cycle theampoule is highly probable of rupturing.

Many problems of compounding additional materials are specific to eachmaterial, and its intended subsequent use. Important compounds are ZnTe,CdTe, and presaturated CZT solvent used to grow large-grained CZTcrystals. Each of these is briefly summarized. The greater the qualityof polycrystalline compounded material the greater the chance ofsubsequently re-crystallizing it into excellent single crystal material.

An example of a compound requiring a very high temperature is ZnTe. Themelting point of zinc telluride is ˜1239° C., so compounding ZnTe viadirect melting would require expensive coated quartz ampoules or highertemperature crucibles, which are prone to contaminate their contentswith heavy metals.

CdTe is an important compound for detectors and energy conversiondevices, and has a melting point above the desired crystallographicphase. It also decomposes/evaporates on melting. Sealed, single use,ampoules are necessary to contain the pressures generated. Excess Te asa solvent is frequently used to reduce the reaction temperature but thisslows the rate of reaction and triggers other problems.

A Te rich CZT solvent formulation can be used for growth of CZTcrystals. Preparing this formulation having excess Te, by conventionalmethods, results in inhomogeneity and improper stoichoimetry, forexample saturating the Te solvent with standard feed that has a Cd/Znratio of 9:1 has two disadvantages. Firstly, it means using moreexpensive synthesized feed rather than the elements, and secondly theCd:Zn ratio is not the equilibrium value and causes instabilities and Zninhomogeneities in the subsequent process.

Cost issues due to slow processes and high cost reactor equipment arecommon to the previous conventional compounding techniques.Contamination from reactor vessel leachate and oxides are also a commonproblem.

Techniques used to stabilize the compounding of other highly reactivematerials in other industries frequently are inapplicable with respectto semiconductors, especially CZT, CdTe and ZnTe.

SUMMARY

According to one aspect of the present invention, a method ofcompounding, homogenizing and consolidating compounds is provided, oneselected from the group of compounds with either very high meltingpoints, or non-congruent melting points, or which decompose on meltingdue to volatile components, or have a melting point above the desirablecrystallographic phase, and including at least a first component and asecond component, and using a reactor and a cold-walled ampoule with gasline coupling, and charge container; the steps as described below:

Supplying in a charge container, at least one volatile or reactive firstsolute component and a second solvent component in a ampoule in a firstlower region, such that the charge container is coupled inside theampoule in a second upper position, separated from a lower region, and aflowing hydrogen gas environment following vacuum evacuation of saidampoule and charge. Placing the ampoule in a reactor having upper andlower heating zones such that temperature in each zone is independentlycontrollable, in a position such that the upper and lower regions of theampoule are matched to the upper and lower heating zones of the reactor.Then, raising the lower reactor zone temperature such that the secondcomponent is liquid and the first component is soluble in the secondcomponent. Then raising the upper reactor zone temperature such that theat least one first solute component is melted and added to the secondsolvent component at a rate such that resulting vapor pressure from theexothermic reaction of mixing is absorbed in a flowing hydrogenenvironment continuously passing through a surge tank, and maintainingtemperature until at least one first solute component has completelymelted and mixed with the second solvent component. Rapidly raising thelower reactor zone temperature above the temperature required fortotally melting the compound and maintaining same for a short duration.Then rapidly quenching at room temperature by removing the ampoule fromreactor.

The method may be conducted with at least one region of the cold-walledampoule is maintained continuously at a lower temperature, such asambient room temperature, and the first and second components aresynthesized in the form of a homogeneous and consolidated compoundmaterial.

According to another aspect of the present invention, a method ofcompounding, homogenizing and consolidating compounds is provided, oneselected from the group of compounds with either very high meltingpoints, or non-congruent melting points, or decomposing on melting dueto volatile elements, or have a melting point above the desirablecrystallographic phase, and including at least a first component and asecond component, and using a reactor and cold-walled ampoule with gasline coupling; the steps as described below:

Supplying in a cold walled ampoule, at least one volatile or reactivefirst component and a second component, with the proportions of thecomponents in the charge being such that the second component is used asa solvent, and a flowing hydrogen gas environment following vacuumevacuation of the ampoule and charge. Placing the ampoule in a reactor.Raising the reactor temperature such that the second component is liquidand the first component is soluble in said second component. Translatingthe cold-walled ampoule such that said charge in said ampoule shows acold point where the solidification of the compound takes place, at arate <10 mm/day, until said charge is solidified. Separating thesolidified compound from the solvent remainder. The method havingconditions wherein at least one region of said cold-walled ampoule ismaintained continuously at ambient room temperature, and the first andsecond components are synthesized in the form of a homogeneous andconsolidated compound material.

According to another aspect of the present invention, a method isprovided of compounding, homogenizing and consolidating ZnTe compounds,using a reactor and cold-walled ampoule with gas line coupling, andcharge container; the steps as described below

Supplying elemental Zn in a charge container, and Te in an ampoule in afirst lower region, such that the charge container is coupled inside theampoule in a second upper position, separated from said lower region,and a flowing hydrogen gas environment following vacuum evacuation ofthe ampoule and charge. The vacuum is backfilled with hydrogen thatcontinues to flow throughout the process. Placing the ampoule in areactor having upper and lower heating zones such that the temperaturein each zone is independently controllable, in a position such that theupper and lower regions of the ampoule are matched to the upper andlower heating zones of said reactor. Raising the lower reactor zone tosubstantially 700° C., such that the Te is molten. Raising the upperreactor zone temperature quickly to substantially 600° C. such that theZn is melted and added to the Te solvent at a controlled drip rate untilall the Zn is dripped into and reacted with the Te to form ZnTe, whichis dissolved in the Te. Translating the cold-walled ampoule such thatthe solution in the ampoule shows a cold point where the directionalsolidification of the compound takes place, at a rate of <10 mm/day,until the solution and solute is solidified. The conditions beingwherein at least one region of the cold-walled ampoule is maintainedcontinuously at ambient room temperature, and the Zn and Te aresynthesized in the form of a homogeneous and consolidated stoichiometricZnTe.

According to another aspect of the present invention, a method isprovided for compounding, homogenizing and consolidating compounds,using a reactor and cold-walled ampoule with gas line coupling, thesteps as below.

Supplying in a cold-walled ampoule, Cd, Zn and Te, with the proportionsof the components in the charge being such that the Te is used as asolvent in excess, and a flowing hydrogen gas environment followingvacuum evacuation of the ampoule and charge. Placing the ampoule in areactor. Raising the reactor temperature such that the Te is liquid andthe Cd and Zn are soluble in the Te. Rapidly raising the reactor zonetemperature above the temperature required for at least 100% solubilityof the Cd and Zn in the Te solvent, totally dissolving the compound andmaintaining for several hours. Rapidly quenching the ampoule to roomtemperature by removing from the reactor. The method having conditionswherein at least one region of the cold-walled ampoule is maintainedcontinuously at ambient room temperature, and the Cd, Zn and Te producea homogeneous and consolidated presaturated solvent material.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B and 1C are schematic side cross sectional views of theVESSEL APPARATUS: FIG. 1A shows an ampoule, FIG. 1B shows a drip cup,and FIG. 1C shows the drip cup positioned in the ampoule as used in themethods of the embodiments of the invention.

FIG. 2: METHOD OF PREPARING CZT USING EXCESS SOLVENT AND TRANSLATION:This figure shows the steps of a method of compounding, homogenizing andconsolidating CZT in a controlled reaction with excess solvent.

FIG. 3: METHOD OF PREPARING CZT USING CONTROLLED ADDITION: This figureshows the steps of a method of compounding, homogenizing andconsolidating CZT by a controlled addition of Cd and Zn into Te solvent.

FIG. 4: METHOD OF PREPARING A PRESATURATED SOLUTION OF CZT WITH EXCESSTE: This figure shows the steps of an embodiment to prepare apresaturated solution of CZT.

FIG. 5: DETAILED METHOD OF PREPARING A PRESATURATED SOLUTION OF CZT WITHEXCESS TE: This figure shows the detailed steps of an alternateembodiment to form a presaturated solution of CZT.

FIG. 6: METHOD OF PREPARING ZnTe USING CONTROLLED ADDITION: This figureshows the steps of an embodiment for compounding, homogenizing andconsolidating ZnTe using a controlled addition of Zn into Te solvent.

FIG. 7: METHOD OF PREPARING CdTe USING DRIP ADDITION: This figure showsthe steps of an embodiment for by compounding, homogenizing andconsolidating CdTe using a controlled addition of Cd into Te solvent.

FIGS. 8A and 8B: REACTOR APPARATUS (SINGLE ZONE FURNACE): These figureschematically show the side cross section and top views, respectively,of the reactor designed to accommodate and heat the ampoule shown inFIG. 1A.

DETAILED DESCRIPTION OF THE INVENTION

The following methods have been created to produce semiconductorcompounds similar in quality to those made by conventional VerticalGradient Freeze (VGF) methods but at much reduced costs, much faster andwith a much reduced probability of explosion. CZT is normallysynthesized from the three elements Cd, Zn and Te using the Bridgman orVertical Gradient Freeze (VGF) process that requires long duration incomplex multi-zone furnaces with sealed hot-walled containment or veryhigh pressure inert gas vessels. The furnace in the disclosed methods isonly operated at VGF-type high temperatures for a few minutes instead ofmany days, thus increasing furnace life dramatically and reducingoperating costs. The cold-walled process, which uses a two- orthree-zone furnace, can produce near-stoichiometric CZT (internal feedfor subsequent crystal growth), polycrystalline, near-stoichiometric,pre-compounded CdTe for potential use in solar cell and otherapplications, and compounded ZnTe useable as feedstock for a thin filmdeposition reactor for use in IR optics and thin film solar cells.

The present inventors have discovered initially how to processpre-saturated solvent prepared in a few hours at atmospheric hydrogenpressure in a cold-walled vessel. The presence of significant Te inexcess of the CZT stoichiometric requirement helps to control theviolence of the exothermic synthesis activity thus eliminating the risksof ampoule rupture. The same methodology is applied to creating CZT feedwhen no excess Te is desirable. The elemental Cd and Zn can be added tothe Te in a controlled manner via a secondary container (the so-called“Drip” method). The methods can be applied to other semiconductorcompounds from the one of the following characteristic groups which:have very high melting points, have non-congruent melting points,decompose/evaporate on melting due to volatile elements, or have amelting point above the desirable crystallographic phase.

The “Drip” method of making a compound according to one embodimentincludes providing a first liquid material located in a first vessel,such as an ampoule, and a second liquid material located in a secondvessel, such as a drip cup. The liquid materials may be first providedin the solid state and then melted to the liquid state. The methodfurther includes adding the second liquid material from the secondvessel into the first liquid material located in the first vessel whilethe first liquid material is maintained at a temperature above aliquidus temperature of the first material and below a liquidustemperature of the compound of the first material and the secondmaterial. The method further includes maintaining the temperature of thefirst material and the second material above the liquidus temperature ofthe first material and below the liquidus temperature of the compounduntil the second liquid material is mixed with the first liquidmaterial. This requires precise control of the rate of addition, and thedrip method is an example of a controlled addition technique. The methodalso includes homogenizing and consolidating the mixture of the firstliquid material and the second liquid material to form a solid compoundof the first material and the second material.

Thus, unlike the prior art methods of mixing two liquid components of acompound in which the mixing is performed above the liquidus temperatureof the compound, the mixing in the “Drip” method is performed below theliquidus temperature of the compound. However, since the liquidustemperature of the components (i.e., the first and the second materials)is lower than the liquidus temperature of the compound, by maintaining arelatively large amount of the solvent liquid and slowly dripping arelatively small amount of the solute liquid into the solvent, thesolvent-solute mixture does not immediately solidify into the solidcompound, despite being maintained below the liquidus temperature of thecompound.

An “excess solvent” method of making a compound according to anotherembodiment of the invention includes providing a first material and asecond material in a vessel, such that the vessel contains an excess ofthe first material than that required to make the compound of the firstmaterial and the second material. In other words, the vessel wouldcontain an excess amount of the first material after all of the secondmaterial and a portion of the first material combine to form a compound.The method also includes heating the first and the second materials to atemperature above a liquidus temperature of the first material and belowa liquidus temperature of the compound of the first material and thesecond material to melt the first material to form a solvent, such thatthe second material forms a soluble solute in the first material. Themethod also includes homogenizing and consolidating the mixture of thefirst material and the second material to form a solid compound of thefirst material and the second material.

Thus, unlike the prior art methods of melting two solid components of acompound above the liquidus temperature of the compound in order to mixthe components, the melting in the excess solvent is performed below theliquidus temperature of the compound. However, since the liquidustemperature of the components of the compound is lower than the liquidustemperature of the compound itself, by maintaining a relatively largeamount of the solvent liquid compared to a relatively small amount ofthe solute liquid, the solvent-solute mixture does not immediatelysolidify into the solid compound, despite being maintained below theliquidus temperature of the compound.

The following definitions and equivalents apply to the embodiments:

-   -   Furnace: maybe called a reactor system or heater system, and        typically includes a heater coil or coils, thermocouple or        thermocouples and temperature controller or temperature        controllers for programmed thermal cycles.    -   Ampoule: a tube type of a vessel, such as a cylindrical tube        (equivalent to a crucible).    -   Liquidus: this temperature is used synonymously with “melting        point”, but can also be used to mean the temperature at which        the material is all liquid, rather than semi-solid or solid, for        compounds which have different liquidus and solidus        temperatures.    -   Quench: rapid cooling of molten compound.    -   Cold-walled vessel process: a heating process using a vessel,        such as an ampoule, having a portion at a lower temperature than        a melting point of the elements being melted, for example room        temperature, as opposed to a hot-walled vessel process in which        the entire ampoule is sealed and heated overall to high        temperatures, possibly for long durations, above the melting        points of the elements. The vessel is preferably an “open-tube”        type vessel in that the vessel is not permanently sealed, but        has a removable cap seal through which vacuum can be created and        ambient flowing gas introduced. The cooled or lower temperature        portion of the vessel is preferably the upper end-cap region, as        it is desired to maintain the seal integrity which can be        damaged from high-temperatures or volatile vapors. Typically,        the maximum temperature range for the lower temperature portion        is such that the volatile element has insignificant vapor        pressure, such as a pressure of 1 torr (1 mm of mercury or        0.001316 atmospheres) or less. For example for cadmium, at        temperatures less than 200 degrees Celsius, the vapor pressure        is much less than 1 torr. While the examples herein use room or        ambient temperature for the cooled portion, the process can work        within the higher range described, such as 25 to 200 ° C., for        example. Thus, a portion of the vessel which is located adjacent        to the inert gas flow inlet, such as adjacent to the gas line        which provides the inert gas flow is maintained at a temperature        of 200 ° C. or less, such as room temperature to 75 ° C. For a        capped open tube type of vessel in which the gas line is        connected to the cap rather than to the vessel, the term        “adjacent to the gas line” includes a portion of the vessel        which contacts the cap.    -   Solvent: the solvent should have a temperature dependent        solubility, hence temperature of the solution can be reduced        well below the total melt temperature. An example of this is        that Te is a solvent for CdTe, ZnTe, and increasing the amount        of Te proportional to CdTe and ZnTe can reduce the liquid state        by several hundred ° C. in the example of CZT.    -   Inert gas: is any gas which does not substantially react with        the materials being processed in the vessel. For example, the        gas may comprise a noble gas (i.e., argon, helium, etc.),        nitrogen, as well as gases which are normally reducing, such as        hydrogen, forming gas, etc, but are not reactive with the        materials being processed.    -   Compounding: may be called synthesis. In the case of CZT, the        compounding forms a binary of CdTe and ZnTe from the elements.

There are two stages in the embodied methods, firstly synthesizing thecompounds and controlling the exothermic reaction of the elements and,secondly, homogenizing and consolidating the synthesized compounds.

The first stage of the cold-walled vessel process effectively uses oneof the elements as a solvent and at least one other element as thesolute, with a critical pressure buffer feature of ambient hydrogen flowduring the treatment. A first method for this stage is a controlledaddition process, or drip method, in which the solvent is heated toliquid in a vessel holding at least one volatile element, which is addedto the solvent in small portions in a controlled manner such that theinstantaneous reaction of the mixing of the limited solute amount isacceptably stable and is not a runaway process. An example would be Teas the solvent and CdZn as the solute, for which Te has a temperaturedependent solubility. The controlled addition process allows theresulting solution to be near-stoichiometric, without any excess of Te.One of the cold-walled vessel variants is to produce CdTe by thecontrolled addition method. If desirable it (controlled addition) can beused for synthesizing and consolidation of ZnTe, CdTe and CZT. Thesenon-solvent processes (drip addition) require a temperature spikedescribed later. However, particularly in the case of ZnTe, therequirement of temperature spike exceeding 1240° C. is not attractiveand a special case is described.

A second method for the first stage is using an excess of solvent andheating a mixture of all elements. For Te as the solvent and CdZn as thesolute, as the Te temperature is increased the CdTe and ZnTe isdissolved well below the total melting point of the constituentsallowing a cold-walled vessel to be used, and the excess solventcontrols the reaction of the solute. Controlling the degree of reactioneliminates the need for expensive explosion-proofing of the reactorsystem, and improves safety. The pressure of volatile elements iscontrolled by an ambient pressure of hydrogen in the cold-walled vessel,and does not require the entire vessel to be at the same temperature. Byexample, for Te as the solvent and Cd as the solute, solutions rich inTe have low partial pressures of Cd and Te, which is advantageous forcontrolling the process and enables use of a “cold-walled” arrangementwith ambient pressure of a gas.

For both of these methods in the first stage of synthesis, the productis neither homogeneous nor consolidated. For the drip-method synthesis,it could be likened to a solid sponge-like mass. It is CZT that is anon-homogeneous and poorly consolidated solid with voids.

For the CZT material example, the details of this first stage includethe following. The elemental Cd and Zn are added to the already moltenTe at a controlled rate with a critical pressure control device torelieve transient over-pressure in the ampoule, i.e. a hydrogen flowcontinuously passing through a reversible flow silicone oil bubbler orsurge tank. It should be noted that any other suitable pressurerelieving devices may also be used. During the extremely exothermicsynthesis, the shock of alternating evacuation and pressure generationis moderated by a surge tank (with oil) coupled to the gas linesattached to the cap of the cold walled vessel. The synthesis rate isobservable by monitoring the oil bubbling activity visually. The Cd andZn drip control is regulated by the area of holes in a suspended dripcup, and the temperature of the upper furnace zone. The process provideshydrogen reduction of the molten Te prior to the Cd/Zn heating and alsoany Cd or Zn oxides will remain in the cup. The Cd/Zn are dripped intothe molten Te reservoir held in a range of 500-800° C.

The second stage of the cold-walled vessel process homogenizes andconsolidates the compounds created by the first stage by one of twomethods (i.e., by the Drip or the excess solvent methods), as follows.By way of an illustrative example of what is taught by this secondstage, a 2″ diameter CZT consolidated ingot from the synthesis phase canbe placed in a 3″ ampoule and heated to a temperature and duration atwhich the compound melts, and is then cooled to consolidate in a 3″diameter form of solid, uniform CZT. This consolidation andhomogenization process is valuable for recovery and recycling of smallpieces of scrap or off-specification CZT.

For the case of the first stage using an excess of Te solvent (i.e., theTe excess solvent method), the second stage method is preferablytranslating the compound such that the solvent is separated to a heatedarea and the homogenized and consolidated compound freezes as it iscooled. Translation means to directionally freeze the melt in thefurnace. This latter non-quenched final stage would be expected to haveless internal voids but would not be as compositionally homogeneous. Tominimize the CZT sublimation loss, it is desirable not to hold thematerial molten for long periods. In this case with the presence ofexcess Te, the material is heated to 900° C. (as opposed to the 1100° C.when there is no excess Te), and under this condition there is some slowevaporation of Te which is not detrimental to the process. The vessel isthen translated such that the solution in the bottom of the vessel ismoved to a cold region where the nucleation and the growth of thematerial takes place. Typically the rate of translation will varydepending on the compound. For CZT, a rate of approximately 2 mm/day isappropriate and many days are required to grow a sizable bulk feedsample. Following translation, the solvent can be extracted from thehomogenous and consolidated crystal compound. For subsequent crystalgrowth using the produced CZT feed it is beneficial to have void-freefeed with a density similar to the crystal to be grown.

For the case of the first stage using the Drip method, the second stageof homogenizing and consolidating has two variants. After all thevolatile element is dropped into the solvent, the solution is still nothomogenous, requiring an additional heating at elevated temperature tomix the elements to near-stoichoimetry. This method is suited for arapid compounding process that maintains stoichoimetry of the elementsin the compound, which is advantageous for a range of crystal growthprocesses. The compound can be heated very rapidly, temporarily inexcess of the melting point for several minutes, to melt completely thecompound. The ampoule is then rapidly quenched at room temperature. Notethat this is not equivalent to melt growth durations, which may be up to15 days. The short temperature spike ensures that the CZT compound ishomogeneously mixed, and the short duration limits undesiredstoichiometric changes due to vaporization. As opposed to a slow quench,the rapid quench freezes the homogeneity throughout the bulk ingot. Analternate variation combines Drip feed addition with an excess of Te inthe first synthesis phase, followed by translation separation in thesecond phase.

For the CZT material example, a description of this second stagefollows. On completion of the synthesis as indicated by the hydrogenflow having returned to the steady rate, the temperature of the bottomTe zone is increased to about 1130° C. Once the charge is observed tohave been completely molten for approximately 5 minutes, and thereforefor homogenization to have occurred, the ampoule is quenched to roomtemperature by its removal from the furnace. Thus, the homogenizationstep is preferably conducted for 10 minutes or less, such as about 3-7minutes.

These cold-walled vessel methods of preparing compounds operateprimarily at temperatures substantially below the total meltingtemperature, representing a dramatic improvement over the known art. Thevery short temperature spike above the compound melting point is used asa secondary homogenization treatment.

An advantage of the cold-walled vessel processes is that an economicaland simple apparatus can be used. The reactor and vessel apparatus issomewhat similar for the various process embodiments herein. Differenceswill be described in each process where necessary.

Due to the features and benefits described, the cold-walled vesselprocess for compounding, homogenizing and consolidating semiconductorcompounds is demonstrated to enable a) economical production of highquality, large-scale CZT, CdTe and ZnTe polycrystalline feedstock inshorter times and using less expensive reactors, b) low temperaturegrowth from non-congruent melting materials such as CZT and CdTe, c)reduction of contamination and vapor pressure related problems ofstandard melt growth methods, d) improved homogeneity of constituentsfor enhancing subsequent single crystal growth, e) elimination of highcost explosion-proof furnace apparatus required for melt growthprocesses.

Apparatus

A cylindrical quartz ampoule 1 for cold-walled vessel compounding isshown in FIG. 1 a, with two tapered regions 3, 4, a lower tapered region3 ending in a flat bottom 2, and an upper tapered region 4. The lowertapered region 3 can be vacuum formed and the upper tapered region canbe a second tube fused onto a first tube with the lower tapered region.For non-Drip addition examples, the same ampoule is used. A cap withvalve assembly (not shown) is couplable to the top of the ampoule forproviding vacuum and a flowing hydrogen environment. Connected to thegas lines is a critical pressure dampening device (not shown) to relievetransient over-pressure in the ampoule. This could take the form of areversible flow silicone oil bubbler or surge tank through which thehydrogen flows. Alternatively the hydrogen can continuously pass througha surge tank, having a second reservoir to ensure the oil does not getsucked into the ampoule during the evacuation cycle. The secondaryreservoir tap drains back into the main bubbler when the flow is normal.Other methods of pressure dampening known in the field can besubstituted.

A cylindrical quartz compounding cup 96 (FIG. 1 b) is designed to fitinside the upper portion of the ampoule and has a curved bottom thatseats within the upper tapered region 4 of the ampoule 1 when both areplaced vertically. The cup 96 is open at the opposing end 93. The curvedbottom portion has two holes, a central hole 95 (5 mm) and an angledhole 94 at 45 degrees to the cylinder axis. An example of the quartzspecification for both can be GE124 semiconductor grade. It is desirablethat there be a small gap between the cup and upper tapered zone toallow gas exchange with the top opening of the ampoule, and preventpressure buildup during the reaction. In general, standard cleaning andhandling techniques are used when preparing the charge materials andloading the ampoules and/or cup.

FIG. 1 c illustrates the Drip method in which the cup 96 is providedinside region 4 of the ampoule 1. The solute 52, such as Cd or ZnCd, ismelted in the cup 96 and is dripped down through holes 94, 95 into thesolvent 51, such as Te, located in region 3 of ampoule 1. The ampoule islocated inside a two heater zone 14 a, 14 b furnace 10. Each zone'stemperature is separately controllable. Zone 14 a is used to heat region3 and zone 14 b is used to heat region 4 containing cup 96. The cap withvalve assembly 61 is coupled to the top of the ampoule 1 for providingvacuum and a flowing hydrogen environment. Connected to the gas lines 62is the critical pressure dampening device 63 to relieve transientover-pressure in the ampoule.

Any suitable furnaces can used in the cold walled vessel processes whichcan provide the desired amount of heat. For example, relatively standardfurnaces can be used as precision control of interface temperature isnot required. A basic single zone furnace 10 is shown in FIGS. 8A and8B. A heater coil and core 14 is centered in the furnace having an innerdiameter slightly larger than the ampoule 1, and surrounded by aninsulating block 22 and 20, which can be made of any thermallyinsulating materials, such as fiberfrax and duraboard portions,respectively. The block may be topped with a thin layer of metal 18,such as aluminum. A liner tube 24 protects the ampoule from touching theheater core. The Drip-addition processes require independentlycontrolled two heater zones (as shown by elements 14 a, 14 b in FIG. 1c) which is achieved by simply stacking two single zone furnaces 10, andsimilarly for three zone furnaces. Each heater zone 14 has athermocouple 12 to allow for microprocessor control of the heating setpoints and heating and cooling rates. An electrical box 26 is connectedby lead wires to the control system such as a computer or othermicroprocessor control logic. No special explosion-proof safetyequipment is necessary for the furnace 10. For processing CZT, since thefurnace only operates at the 1100° C. temperature for less than 10minutes during homogenization, such as for about 5 minutes, instead ofmany days the furnace life is increased dramatically. For thecold-walled compounding versions that require translation of theampoule, the furnace and ampoule have a translation motor and linearbearing stage (not shown) for relative positioning of the ampoule atgrowth rates 0.01 to 10 mm/day depending on the compound. Translationsystems commonly used in crystal growing industry, are suitable. Otherfurnace types, including RF and optical heating type furnaces may alsobe used.

Five detailed examples will illustrate embodiments of the cold-walledvessel methods for specific compounds, that result in suitable feedstockfor subsequent growth of large dimensioned bulk single crystal enablinghigh performance radiation detector applications and the like,fabricated from the single crystals. The methods selected for the twophases; of synthesis first then homogenization/consolidation, aredescribed as appropriate to the compound being prepared. Five examplesof the embodied methods are shown in Table 1 below for key materials ofinterest, CZT, CdTe, ZnTe and CZT with excess Te formulated as a Te-richsolvent for subsequent growth processes. In general, the processes witha rapid quench result in near-stoichiometric compound, and thenon-quenched processes result in compounds substantially closer tostoichiometric. Herein, the terms near-stoichiometric and stoichiometricwill be used respectively, but the term stoichiometric is not intendedto mean perfectly stoichiometric. TABLE 1 Cold-walled Vessel CompoundingProcesses and Treatments Synthesis and Method of ControllingHomogenizing and Compound Exothermic consolidation Quench FIG. TypeReaction Method Type 2 Stoichiometric Excess solvent Translation NoneCZT separation 3 Near- Drip addition Temperature spike Rapid AirStoichiometric above MP of CZT Quench CZT 4, 5 CZT - excess Excess TeTemperature spike Rapid Air Te above MP of CZT Quench 6 ZnTe Dripaddition Translation None (Te solvent) separation 7 CdTe Drip additionTemperature spike Rapid Air above MP of CdTe Quench

The cold-walled vessel method illustrated in FIG. 2 is for preparingstoichiometric CZT. The method of controlling the exothermic reaction isby using an excess of Te solvent. An example of the formulation of thecharge materials demonstrates the excess; Cd: 101.18 gm Zn:  9.51 gm Te: 644.6 gm

In step 40, the charge formulation is supplied as the above example,prepared in the ampoule 01 and sealed with a top cap (not shown). Theampoule 01 is pumped down to high vacuum through the valves in the topcap, then flowing hydrogen gas is introduced. Standard cleaning andhandling techniques are used when preparing the materials and loadingthe ampoule and drip cup. In step 42, the ampoule is placed in thefurnace. In step 44, the furnace 10 temperature is increased such thatthe entire charge is heated simultaneously at the start of the process,above a temperature and for a duration in which the constituents aremixed. Specifically for CZT, the charge is heated to ˜900° C. at aheating rate of 25-50° C./hr, then allowed to soak at that temperaturefor 2 days to allow for mixing. Next, in step 46, the bottom of theampoule is translated slowly out of the heating zone, such that thepolycrystalline CZT cools and solidifies as the excess Te is drawn tothe heated area. A typical translation rate is 2 mm/day. At this rate atypical feed amount is synthesized after approximately 18 days. In step48, following furnace cool down, the excess Te is separated from thecompound. This embodiment of the compounding process produces highquality stoichiometric CZT feed suitable for use in crystal growthprocesses. The process is lengthy and, therefore, costly.

The compounding method shown in FIG. 3 is for preparingnear-stoichiometric CZT. The method of synthesis in the first stage iscontrolling the exothermic reaction by the Drip addition method. Themethod of homogenizing and consolidating is by a rapid heating spikeabove CZT's melting point. An example of the formulation of the chargematerials is below; Cd: 192.9 gm Zn:  12.5 gm Te: 248.5 gm

For the cold-walled vessel process of preparing CZT polycrystallinefeed, starting in step 50, a charge of Te and dopant is placed in thebottom of the ampoule 01. Then in step 52, elemental Cd and Zn areplaced in the drip cup 96 which is then positioned in the upper taperedzone of the ampoule 01. The ampoule is sealed, evacuated to a vacuum andthen flowing hydrogen gas is introduced in step 54. Standard cleaningand handling techniques are used when preparing the materials andloading the ampoules and cup. Next in step 55, the ampoule 01 with dripcup 96 is positioned in the two zone furnace (not shown), such that thelower portion 03 of the ampoule is positioned in a first heater zone(not shown) and the second heater zone is located at the drip cup 96.

Next, the bottom 03 and upper 04 tapered zones are heated separatelysuch that the Cd and Zn are slowly melted and “dripped” through the cuphole 95 by gravity and drops into the molten Te in the bottom of theampoule 01, in a controlled addition process. The Cd and Zn are togetherin the second zone. The Cd is the lower melting point and dripsfirst—the Cd and Zn melting points are 321° C. and 420° C. respectively.The Zn and ZnTe follow the Cd melt, and there may be some alloyformation in the cup prior to drip. The slow incremental addition ofsmall amounts of Cd and Zn in this case does not require a vacuum sealor evacuation of byproduct gases. An advantage of the process is that Cdand Zn surface oxides are left on the cup surfaces. The angled hole indrip cup 96 allows for pressure equilibrium between the lower reactionzone of the solvent and area above the cup in the ampoule. Thedimensions of the ampoule and cup holes are demonstrative of an operableapparatus, but may be varied within the constraint that the reaction ofthe drips is controllable. In contrast to the single heater zone of thefirst embodiment, the drip feed requires two independent heater zones(not shown), one for the lower portion of the ampoule and one for theupper cup region of the ampoule, which can easily be provided bystacking two furnaces 10 with independent temperature control for each.An alternative that may produce better drip addition control, would beto use a premade Cd 10% Zn alloy (having melting point ˜375° C.),however there are practical complications to making and quenching ofthis alloy that make the prior method the preferred method.

In step 56, the lower heater is heated rapidly to 750° C., melting theTe solvent, note that due to the flowing hydrogen, the process hashydrogen reducing the molten Te surface. In step 58, the upper heater isheated quickly to 750° C. triggering the Cd and Zn to melt at acontrolled rate. This rate is determined empirically by trial and errorand manually observing the strength of reaction at various drip ratesand hole sizes. It has been found that dropping large chunks of Cd andZn is not controllable. The hole size of the cup at 5 mm, with thespecified operating temperature, was found to work well. The heatingcontinues until all the charge materials in the upper cup have droppedinto the solvent.

The materials are now mixed but not homogenous or consolidated. Toaccomplish this the mix is heated above the melting point of the CZT andmaintained for approximately 2 min as shown in step 60. Note, that thisis a much smaller period of time than VGF or alternate melt compoundingmethods, which remain “hot walled” for extended periods of many days.Finally, in step 62, the ampoule is air quenched by removing it from thefurnace. The hydrogen gas is still flowing, and the ampoule can becooled on a stand in a box with circulating air. The quenched ingot hasthe correct near-stoichiometry to act as high quality CZT feed for theTHM process. The resulting ingot is comparable in quality to VGFcompounded material but has been produced much more quickly, in far lessexpensive apparatus and a much lower risk of explosion.

An alternate version of this process was developed briefly with thefollowing modifications;

-   -   In Step 56 heat from room temp to 580° C at 200° C./hr heating        rate and soak for 4 hours.    -   In the homogenizing heating phase, Step 58, raise temperature to        890° C. at 25° C./hr and hold for 1 hour. This phase allows for        more complete mixing of the constituents, so the boule is        suitable as high quality feedstock for crystal growing        processes.    -   Step 60 raise the temperature to ˜1100-1120° C. and hold there        for 10 minutes.

The temperature ranges given are relative to one embodiment. Thedescribed furnace and ampoule configuration were designed so that therate of melt is suitably slow so as to not cause a runaway reaction inthe Te solvent. Other ranges and temperature cycles may be applicablefor other furnace, ampoule and cup configurations, and be within thescope of the invention. The furnace is selected so that the heating rateof change is slow. The heater of the example embodiment has a powerrating of 2000 watts. This heating cycle can be controlled automaticallyby a heater controlled with calibrated thermocouples, and the cycle setpoints are determined empirically.

The cold-walled vessel process shown in FIG. 4 is for preparing apre-saturated solvent formulation of CZT with excess Te for use in a THMcrystal process. For this process, the Te does not have to be separatedand the entire charge is quenched. The synthesis method controls theexothermic reaction using an excess of Te, and the homogenizing methodis a temperature spike above the melting point of CZT (1100° C.). Anextended heater zone (not shown) is used to heat the entire charge. Anexample of the formulation of the charge materials is below; Cd: 130 gmZn:  6 gm Te: 641 gm

In step 70, all charge materials are loaded in the ampoule and theampoule 01 is sealed with the top cap (not shown). The ampoule is pumpedunder vacuum and ambient hydrogen gas is introduced. The ampoule isplaced in a furnace in step 72. In step 74, the furnace temperature isincreased such that ampoule is heated to 580° C. at 200° C./hr andsoaked for 4 hrs, creating a liquid phase of the Te solvent. Thehomogenizing heating is done in step 76, rapidly heating the ampoulebeyond the temperature resulting in 100% solubility. In this example,heating to 890° C. at 25° C./hr and soaking for 1 hour. The ampoule isquenched rapidly to room temperature in step 78. The total elapsed timeis only several hours, resulting in efficient low cost production.

A detailed embodiment is shown in FIG. 5 to prepare the same formulationused in FIG. 4 method, showing the additional steps of cleaning andprocessing. The quartz ampoule is cleaned by etching, and the caps andvalves are cleaned in step 30. The ampoule and caps are assembled forbaking in step 31. The ampoule is baked for 150 minutes under low vacuumin step 32. Charge materials are cut and weighed to formulation in step33. The charge materials are added to the ampoule, which is assembled instep 34. The loaded ampoule is flushed under low vacuum in a hydrogenenvironment in step 35. The ampoule is loaded in the furnace and heatedat 200° C./hr to 580° C., soaked for 4 hours, then heated to 890° C. at25° C./hr and soaked for 1 hour. In step 37, the ampoule is air quenchedunder flowing hydrogen until cool. The ingot is removed and sealed instep 38 for further use.

The cold-walled vessel processes shown in FIG. 6 is for preparingstoichiometric ZnTe, and operates far below its melting point of 1300°C., while maintaining desired stoichiometry, so that the ingot can beused as feedstock for a wide range of commercial applications. Thesynthesis method is the Drip addition method with an excess of Te. Themethod of homogenizing and consolidation is by translation separation.As discussed in the previous Drip-addition process, a two-zone heater isrequired. An example of the of the charge materials is below; Zn:  70 gmTe: 106 gm

In step 80, the solvent Te charge is loaded in the lower portion of theampoule 01. Next in 82, loading Zn into the quartz drip cup 96, seatingthe cup in the upper portion of the ampoule 01 and sealing the ampoulewith a top cap (not shown). The ampoule is pumped under vacuum andflowing hydrogen ambient gas introduced. In step 84 the ampoule isplaced in a two-zone furnace (not shown) such that upper and lowerregions of the ampoule match the upper and lower zones of the furnace,which can be independently heated. The lower portion of the ampoule 01with Te is rapidly heated to 700° C. in a two-heater furnace in step 86,melting the Te solvent entirely. The Zn in the drip cup 96 is melted ata controlled drip rate by heating the upper portion of the ampoule 05 inthe upper furnace or heater, to 600° C., until all the Zn has melted. Instep 90, the lower portion of the ampoule is rapidly heated by the lowerheater, to 900° C. at 75° C./hr, followed by translation of the ampoulerelative to the furnace at ˜7 mm/day to separate the solvent.Alternatively, for the translation process, the ampoule may betransferred to a translating furnace setup from the original two-stageheater furnace.

The cold-walled vessel method shown in FIG. 7 is for preparingnear-stoichiometric CdTe, at temperatures far below melting point of˜1100° C., while maintaining desired stoichiometry, so that the ingotcan be used as feedstock for a wide range of commercial applications.The synthesis method is the Drip addition method. The method ofhomogenizing and consolidation is by high temperature spike above themelting point of CdTe. The charge formulation is below; Cd: 323 gm Te:367 gm

With respect to FIG. 7, first the Te is loaded in the lower portion ofthe ampoule per step 100. Then the Cd is placed in the drip cup 96 andthe cup seated in the top portion of the ampoule 01 and sealed with atop cap in step 102. Hydrogen gas is introduced into the ampoule vacuumthrough the cap. In step 104, the ampoule is placed in the two-zonefurnace (not shown) such that the upper and lower portions of ampoulematch the upper and lower heating zones of the furnace, which can beindependently heated. The lower portion of the ampoule is heated quicklyto 750° C. to melt the Te solvent using the lower heating element in106. The cup portion of the ampoule is heated quickly to 750° C., andmaintained until all the Cd has dropped into the Te below in step 108.The first phase of synthesis is now done, ready for the homogenizingphase. In step 110, the lower ampoule portion is rapidly heated abovethe melting point of CdTe, and maintained for 2 minutes to homogenizethe mixture. Finally in step 62, the charge is rapidly quenched in airby removing it from the furnace. The resultant CdTe isnear-stoichiometric and has been produced quickly, typically in lessthan 6 hours.

There are many alternate embodiments for various cold-wall vesselprocesses for compounding, homogenizing and consolidating compounds. Forthe Drip method, there could be multiple holes in the bottom of the dripcup 96 or a automated mechanical method of adding the materials, such asby pellet holders etc. The drip rate may be adjusted for differentproportions of constituents and solvent concentrations, as well asfurnace set points. The shape of the ampoule 01 can also benon-cylindrical (but is preferably symmetric). High purity hydrogen isused but lower purity hydrogen will work as well. Other inert gases suchas argon may be suitable. Various heating, cooling and soak cyclesdifferent from the examples listed may also be used depending on thecompound. The basic premise of the invention is that the synthesishappens at cold-walled temperatures, lower by several hundred degreesthan the relevant melt temperatures. The use of a temperature spiketreatment happens after the primary synthesis.

The advantages of the embodiments described herein include a) the systemdoes not require expensive explosion-proof equipment, b) unexpectedly,the Cd vapour pressure is controlled at low levels during the process,c) when using Zn charge material, zinc oxide in the upper portionremains coated to the walls of the cup and does not contaminate theboule, which can easily be removed, d) the highest temperature longduration soak is >200° C. lower than conventional melt processtemperatures, resulting in much less quartz contamination in the CZTcompound, e) the speed of processing and cooling cycle are a bigimprovement over known compounding processes, f) apparatus advantages:the ampoule and cup can be reused many times in the process,substantially reducing production costs.

In general, the cold-walled vessel processes for compounding,homogenizing and consolidating compounds can be used for CdTe compounds,such as would be useful for solar cells, and can also be used for otherexothermic metal compounds, with appropriate scaling and calibration tocompensate for different chemical properties. The methods can be appliedto a wide range of CZT concentrations, for example changing the Znconcentration from 0 (CdTe) to 0.07 to 0.09 (CZT) depending on theapplication. The process is orders of magnitude faster than thealternate VGF process, which may take many days.

We have discovered a non-VGF process for compounding, homogenizing andconsolidating ZnTe in a cold-walled vessel. The technique was thenapplied to preparing pre-saturated solvent for CZT crystal growth, and arapid quench was used to speed the overall process. Further enhancementswere made to use the process for CZT feed with controlled addition ofthe CdZn using a specialized ampoule system, and again a rapid quench tomaintain properties of the feed. The resulting feed of highlypolycrystalline CZT of uniform composition was suitable to be used in aTHM to grow high quality CZT crystals. Detector devices fabricated fromCZT single crystals grown using feed compounds prepared by the methodsherein resulted in desirable detector response.

The reader will appreciate that the foregoing description is onlyintended to be illustrative of the present invention and is, therefore,not to be construed to a limitation or restriction thereon. Thisapplication claims benefit of priority of Canadian application serialnumber 2,510,415 filed on Jun. 21, 2005 which is incorporated herein byreference in its entirety.

1. A method of making a compound, comprising: providing a first liquidmaterial located in a first vessel and a second liquid material locatedin a second vessel; flowing an inert gas through the first vessel;adding the second liquid material from the second vessel into the firstliquid material located in the first vessel at a controlled rate suchthat resulting vapor pressure surges from an exothermic reaction ofmixing the first material and the second material are absorbed in theflowing inert gas, while the first liquid material is maintained at atemperature above a liquidus temperature of the first material and belowa liquidus temperature of the compound of the first material and thesecond material; maintaining a temperature of the first material and thesecond material above the liquidus temperature of the first material andbelow the liquidus temperature of the compound until the second liquidmaterial is mixed with the first liquid material, while maintaining aportion of the first vessel which is located adjacent to an inert gasflow inlet at a temperature at which a vapor pressure of the secondmaterial is 1 torr or less; and homogenizing and consolidating themixture of the first liquid material and the second liquid material toform a solid compound of the first material and the second material. 2.The method of claim 1, wherein the solid compound comprises a compoundsemiconductor material.
 3. The method of claim 2, wherein the firstmaterial comprises a Group VI material, the second material comprises aGroup II material and the compound comprises a Group II-VI compoundsemiconductor material.
 4. The method of claim 3, wherein the firstmaterial comprises Te, the second material comprises Zn, Cd or ZnCd, andthe compound comprises a ZnTe, CdTe or CdZnTe compound semiconductormaterial.
 5. The method of claim 1, wherein the step of maintaining aportion of the first vessel which is located adjacent to an inert gasflow inlet at a temperature at which a vapor pressure of the secondmaterial is 1 torr or less comprises: maintaining, at a temperature of200° C. or less, the portion of the first vessel which is locatedadjacent to a gas line coupling which provides the inert gas flow. 6.The method of claim 1, further comprising: providing the first materialin a solid state into the first vessel; providing the second material ina solid state into the second vessel; heating the first vessel to meltthe first material into the liquid state; and heating the second vesselto melt the second material into the liquid state.
 7. The method ofclaim 6, wherein the first vessel comprises an ampoule and the secondvessel comprises a drip cup located in the ampoule such that the secondliquid material is controllably added from the drip cup into the firstliquid material located in the ampoule.
 8. The method of claim 1,wherein the step of homogenizing and consolidating the mixture comprisesslowly cooling the mixture by removing heat from the mixture.
 9. Themethod of claim 1, wherein the step of homogenizing and consolidatingthe mixture comprises heating the mixture above the liquidus temperatureof the compound to homogenize the mixture and quenching the mixture toconsolidate the mixture into the solid compound.
 10. The method of claim1, wherein: the compound is selected from a group of compounds whicheither have very high melting points, non-congruent melting points,decompose/evaporate on melting due to volatile elements, or have amelting point above a desirable crystallographic phase, and including atleast a first component and a second component; the first vesselcomprises a cold-walled ampoule containing an inert gas line couplingand a cold portion; and the second vessel comprises a charge containerlocated in the first vessel.
 11. The method of claim 10, wherein themethod comprises: a) supplying in the charge container, the secondmaterial comprising at least one volatile or reactive second solutecomponent, and supplying the first material comprising a first solventcomponent in the ampoule in a first lower region, such that the chargecontainer is coupled inside the ampoule in a second upper position,separated from said lower region, and flowing the inert gas environmentfollowing vacuum evacuation of said ampoule and said charge container;b) placing the ampoule in a reactor having upper and lower heating zonessuch that temperature in each zone is independently controllable, in aposition such that the second upper and the first lower regions of theampoule correspond to the upper and lower heating zones of said reactor;c) raising the lower reactor zone temperature such that the firstcomponent is liquid and the second component is soluble in said firstcomponent; d) raising the upper reactor zone temperature such that theat least one second solute component is melted and added to said firstsolvent component at a rate such that resulting vapor pressure surgesfrom the exothermic reaction of mixing is absorbed in the flowing inertgas environment continuously passing through a surge tank, andmaintaining temperature until the at least one second solute componenthas melted and mixed with the first solvent component; e) rapidlyraising the lower reactor zone temperature above a temperature requiredfor totally melting the compound and maintaining the raised temperaturefor a short duration; and f) rapidly quenching said ampoule by removingit from the reactor; wherein the portion of said cold-walled ampouleadjacent to the inert gas line coupling is maintained continuously atambient room temperature, and said first and second components aresynthesized in a form of a homogeneous and consolidated compoundmaterial.
 12. The method of claim 11, wherein: said ampoule ispositioned vertically in said reactor and said charge container is adrip cup positioned in the upper region of said ampoule, and havingholes in the bottom portion of said drip cup, having effective areasuitable for meeting the rate control condition of step d); and thesecond component comprises Cd; the first component comprises Te; and theinert flowing gas comprises hydrogen.
 13. The method of claim 12,wherein in step c) the lower reactor zone temperature is raised tosubstantially 750° C., in step d) the upper reactor zone temperature israised to substantially 750° C., and in step e) the lower reactor zonetemperature is raised for several minutes to substantially 1130° C.,said method forming a homogeneous and consolidated CdTe compound. 14.The method of claim 12, wherein a third component Zn and a dopantmaterial are supplied in a stoichiometric amount and simultaneouslyprocessed in the same manner as said second component.
 15. The method ofclaim 14, wherein in step c) the lower reactor zone temperature issubstantially 750° C., in step d) the upper reactor zone temperature issubstantially 750° C. and in step e) the lower reactor zone temperatureis substantially 1130° C. for a duration of several minutes, said methodforming a homogeneous and consolidated CdZnTe compound.
 16. The methodof claim 10, wherein the method comprises: a) said ampoule is positionedvertically in a reactor and said charge container comprises a drip cuphaving holes in a bottom portion; b) supplying in the charge container,the second material comprising a Zn volatile or reactive second solutecomponent, and supplying the first material comprising a Te firstsolvent component in the ampoule in a first lower region, such that thecharge container is coupled inside the ampoule in a second upperposition, separated from said lower region, and flowing the inert gascomprising hydrogen following vacuum evacuation of said ampoule and saidcharge container; d) placing the ampoule in a reactor having upper andlower heating zones such that temperature in each zone is independentlycontrollable, in a position such that the second upper and the firstlower regions of the ampoule correspond to the upper and lower heatingzones of said reactor; d) raising the lower reactor zone temperature tosubstantially 700° C. such that the Te first component is liquid and theZn second component is soluble in said first component; d) raising theupper reactor zone temperature to substantially 600° C. such that the Znsecond solute component is melted and added to said first solventcomponent at a rate such that resulting vapor pressure surges from theexothermic reaction of mixing is absorbed in the flowing inert gasenvironment continuously passing through a surge tank, and maintainingtemperature until the at least one second solute component has meltedand mixed with the first solvent component; e) translating thecold-walled ampoule such that a solution in said ampoule shows a coldpoint where the solidification of the compound takes place, at a rate of<10 mm/day, until said solution is solidified; and wherein the portionof said cold-walled ampoule adjacent to the inert gas line coupling ismaintained continuously at ambient room temperature, and said first andsecond components are synthesized in a form of a homogeneous andconsolidated ZnTe compound material.
 17. The method of claim 2, furthercomprising incorporating the compound semiconductor material into asemiconductor device.
 18. A method of making a compound, comprising:providing a first material and a second material in a vessel, such thatthe vessel contains an excess of the first material than that requiredto make the compound of the first material and the second material;flowing an inert gas through the vessel; heating the first and thesecond materials to a temperature above a liquidus temperature of thefirst material and below a liquidus temperature of the compound of thefirst material and the second material to melt the first material toform a solvent, such that the second material forms a soluble solute inthe first material and such that resulting vapor pressure surges from anexothermic reaction of mixing the first material and the second materialare absorbed in the flowing inert gas; during the step of heating thefirst and the second materials, maintaining a portion of the vesselwhich is located adjacent to an inert gas flow inlet at a temperature atwhich a vapor pressure of the second material is 1 torr or less; andhomogenizing and consolidating the mixture of the first material and thesecond material to form a solid compound of the first material and thesecond material.
 19. The method of claim 18, wherein the solid compoundcomprises a compound semiconductor material.
 20. The method of claim 19,wherein the first material comprises a Group VI material, the secondmaterial comprises a Group II material and the compound comprises aGroup II-VI compound semiconductor material.
 21. The method of claim 20,wherein the first material comprises Te, the second material comprisesZn, Cd or ZnCd, and the compound comprises a ZnTe, CdTe or CdZnTecompound semiconductor material.
 22. The method of claim 18, wherein theinert gas comprises hydrogen.
 23. The method of claim 18, wherein thestep of maintaining a portion of the vessel which is located adjacent toan inert gas flow inlet at a temperature at which a vapor pressure ofthe second material is 1 torr or less comprises: maintaining, at atemperature of 200° C. or less, the portion of the vessel which islocated adjacent to a gas line coupling which provides the inert gasflow.
 24. The method of claim 18, wherein the step of homogenizing andconsolidating the mixture comprises slowly cooling the mixture byremoving heat from the mixture.
 25. The method of claim 18, wherein thestep of homogenizing and consolidating the mixture comprises heating themixture above the liquidus temperature of the compound to homogenize themixture and quenching the mixture to consolidate the mixture into thesolid compound.
 26. The method of claim 18, wherein: the compound isselected from a group of compounds which either have very high meltingpoints, non-congruent melting points, decompose/evaporate on melting dueto volatile elements, or have a melting point above a desirablecrystallographic phase, and including at least a first component and asecond component; and the vessel comprises a cold-walled ampoulecontaining a gas line coupling and a cold portion.
 27. The method ofclaim 26, wherein the method comprises: a) supplying in the cold-walledampoule, a charge comprising the second material comprising at least onevolatile or reactive second component of the compound and the firstmaterial comprising a first component of the compound, with a proportionof the components in the charge being such that the first component isused as a solvent, and flowing an inert gas environment following vacuumevacuation of said ampoule; b) placing the ampoule in a reactor; c)raising the reactor temperature such that the first component is liquidand the second component is soluble in said first component; d)translating the cold-walled ampoule such that said charge in saidampoule shows a cold point where the solidification of the compoundtakes place, at a rate of <10 mm/day, until said charge is solidified;and e) separating the solid compound from a remainder of the solventsuch that said first and second components are synthesized in the formof a homogeneous and consolidated compound material.
 28. The method ofclaim 27, wherein said second component is Cd, said first component isTe, and further comprising a third component, Zn, to which is added adopant material, and the three components are in stoichiometric amountsand are simultaneously processed.
 29. The method of claim 28, whereinsaid inert flowing gas comprises hydrogen.
 30. The method of claim 28,wherein, in step c) the reactor temperature is substantially 900° C.maintained for approximately 2 days, and in step d) the translation rateis substantially 2 mm/day and the synthesized, homogenous, consolidatedcompound is CdZnTe.
 31. The method of claim 27, wherein the secondcomponent is Cd, the first component is Te, and the synthesized,homogenous, consolidated compound is substantially stoichiometric CdTe.32. The method of claim 19, further comprising incorporating thecompound semiconductor material into a semiconductor device.
 33. Amethod of making a compound, comprising: providing a solute dissolved ina solvent in a first portion of a vessel; maintaining the first portionof the vessel at a temperature above which the solute is soluble in thesolvent; flowing an inert gas through the vessel such that resultingvapor pressure surges from an exothermic reaction of mixing the solventand the solute is absorbed in the flowing inert gas; maintaining asecond portion of the vessel which is located adjacent to an inert gasinlet at a temperature at which a vapor pressure of the solute is 1 torror less; and solidifying the solvent and solute to form the compound.34. The method of claim 33, wherein the step of providing a solutedissolved in a solvent in the first portion of the vessel comprisesproviding a first solid material and a second solid material into thefirst portion of the vessel and melting the first and the secondmaterial at a temperature below a liquidus temperature of the compound.35. The method of claim 33, wherein the step of providing a solutedissolved in a solvent in the first portion of the vessel comprises:providing a first solid material into the first portion of the vesseland melting the first material to form the solvent; and providing asecond solid material into a second vessel, melting the second materialto form the solute and adding a controlled amount of liquid solute intothe solvent while maintaining the solvent at a temperature below aliquidus temperature of the compound.
 36. The method of claim 33,wherein the step of solidifying comprises homogenizing and consolidatinga mixture of the solvent and the solute to form a solid compound of thefirst material and the second material.
 37. The method of claim 36,wherein the compound comprises a compound semiconductor material. 38.The method of claim 37, wherein the solvent comprises a Group VImaterial, the solute comprises a Group II material and the compoundcomprises a Group II-VI compound semiconductor material.
 39. The methodof claim 38, wherein the solvent comprises Te, the solute comprises Zn,Cd or ZnCd, and the compound comprises a ZnTe, CdTe or CdZnTe compoundsemiconductor material.
 40. The method of claim 36, wherein the step ofhomogenizing and consolidating the mixture comprises slowly cooling themixture by removing heat from the mixture.
 41. The method of claim 36,wherein the step of homogenizing and consolidating the mixture comprisesheating the mixture above the liquidus temperature of the compound tohomogenize the mixture and quenching the mixture to consolidate themixture into the solid compound.